A number of organic synthesis reactions using a transition metal complex as a catalyst have hitherto been developed and made use of for various purposes. In particular, many reports have been made on enantioselective catalysts useful for enantioselective synthesis reactions, such as enantioselective hydrogenation and enantioselective isomerization. Among them, metal complexes in which an optically active tertiary phosphine compound is coordinated to metallic rhodium or ruthenium are well known as catalysts for enantioselective hydrogenation.
For example, a rhodium-phosphine complex using 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl (hereinafter abbreviated as BINAP) as a ligand is disclosed in JP-A-55-61937 (the term "JP-A" as used herein means an "unexamined published Japanese patent application").
Known ruthenium complexes include those having BINAP or a derivative thereof as a ligand, such as Ru.sub.2 Cl.sub.4 (BINAP).sub.2 (NEt.sub.3) (wherein Et represents an ethyl group) as disclosed in Ikariya, et al , J. Chem. Soc., Chem. Commun., p. 922 (1985), Ru(O.sub.2 CR).sub.2 -(BINAP) (wherein R represents a lower alkyl group, a lower alkyl-substituted phenyl group, etc.) as disclosed in JP-A-62-265293, and [RuH.sub.l (R-BINAP).sub.m ]X.sub.n (wherein R represents a hydrogen atom or a methyl group; X represents ClO.sub.4, BF.sub.4, or PF.sub.6 ; when l is 0, m represents 1, and n represents 2; and when l is 1, m represents 2, and n represents 1) as disclosed in JP-A-63-41487.
For further reference to enantioselective synthesis reactions using transition metal catalysts, Sheri. L. Blystone, Chemical Reviews, pp. 1663-1679 (1989) can be referred to.
However, few cases are known in which an iridium-optically active phosphine complex is actually used as a catalyst for enantioselective syntheses, except conversion of an imine to an optically active amine as reported, e.g., in JP-A-63-57558 and JP-A-64-47723.
Rhodium- or ruthenium-optically active phosphine complexes are known to exhibit high catalytic activity on a relatively wide range of substrates to give a high enantioselectivity (i.e., optical purity of a product) in enantioselective syntheses, especially enantioselective hydrogenation. However, both catalytic activity and enantioselectivity achieved by these complexes are sometimes unsatisfactory depending on the reaction substrate. Accordingly, it has been demanded to develop a novel catalyst for enantioselective syntheses.